Portsmouth weather in September 2025

Expect 73°F daytime maximum temperatures in the shade with on average 8 hours of sunshine per day in Portsmouth in September. Check more long-term weather averages for Portsmouth in September before you book your next holiday to New Hampshire in 2025/2026.

  • 73°F maximum daytime temperature in September in Portsmouth73
    73°F max day temperature
  • 8 hours of sunshine per day
  • 8 days with some rainfall in September in Portsmouth8
    8 days with some rainfall
  • 50°F minimum night-time temperature in September in Portsmouth50
    50°F min night temperature
  • 12 hours of daylight per day in September in Portsmouth12
    12 hours of daylight per day
  • No heat & humidity in September in Portsmouth0
    No heat & humidity
  • 3.4 inches monthly rainfall in September in Portsmouth3.4
    3.4 inches of monthly rainfall
  • UV (maximum) index 6 (High) in September in Portsmouth6
    6 (High) UV index
  • 61°F sea temperature in September in Portsmouth61
    61°F sea temperature

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The September weather guide for New Hampshire (Portsmouth) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C)  |  Imperial (°F)

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How hot is it in Portsmouth in September?

Daytime temperatures usually reach 73°F in Portsmouth in September, falling to 50°F at night.

How sunny is it in Portsmouth in September?

There are normally 8 hours of bright sunshine each day in Portsmouth in September - that's 60% of daylight hours.

How warm is the sea around Portsmouth in September?

The average sea temperature around Portsmouth in September is 61°F.

Does it rain in Portsmouth in September?

There are usually 8 days with some rain in Portsmouth in September and the average monthly rainfall is 3.4 inches.

What is the chance of a hurricane in Portsmouth in September?

On average less than 1 day in September in Portsmouth is likely to be affected by the passage of one or more tropical storms.

Portsmouth September sunrise & sunset times

Browse the sunrise and sunset times for Portsmouth in September 2025. Select a month to view Portsmouth sunrise and sunset times for the next 12 months.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 05:08 18:17
Monday, 15th September 2025 05:23 17:52
Tuesday, 30th September 2025 05:40 17:25

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